With FISA Section 702 set to expire at the end of the year, Congress will soon move to a debate over reform and reauthorization for the first time since the Snowden revelations. Undoubtedly, one high-profile reform proposal will be closing the “backdoor search loophole.” Doing so would prohibit government queries deliberately seeking out Americans’ communications without first obtaining a warrant, an essential step forward. Closing the backdoor search loophole alone, however, would still permit the FBI to use Section 702 to jumpstart domestic criminal investigations via keyword queries. Such searches—necessary in the foreign intelligence context—could also be used to return a range of Americans’ communications.

In order to be effective at protecting privacy and due process rights, closing the backdoor search loophole must also be paired with additional restrictions on using Section 702 data for domestic criminal investigations.

Imposing use limits on foreign intelligence information raises legitimate concerns over recreating the “Wall” that was removed after the 9/11-attacks to facilitate information sharing. As I have argued previously, ending the practice of stove-piping and removing the Wall—as recommended by the 9/11 Commission—made sense for the limited goal of sharing foreign intelligence in order to better understand national security threats. The problem is that absent this Wall, Section 702 allows not only for the appropriate sharing of national security information between agencies, but also the problematic unrestricted use of military and intelligence information for domestic law enforcement.

The goal of Section 702 reforms should be to restore a proper balance, achieving security purposes while limiting unnecessary incursions into substantive rights. Allowing Section 702 data to be shared for legitimate foreign intelligence and counterterrorism purposes, and used to investigate and prosecute a limited set of serious crimes, might be a reasonable policy. Permitting domestic law enforcement to access and use that data to investigate any crime is another matter entirely.

The current rules are inadequate to prevent Section 702 information—gathered for foreign intelligence purposes—from being co-opted for domestic policing. Although ODNI created law enforcement use limits for Section 702 in 2015, these rules create broad, non-exclusive exceptions to the ODNI limits and only apply to in-court use of Section 702-derived evidence, with no limit on investigative use. In other words, at least in theory, an investigation for any crime could be built upon warrantless Section 702 surveillance that captured Americans’ communications.

This idea that law enforcement can “poke around” and do anything with lawfully collected information is unreasonable and at odds with basic privacy rights. In passing Section 702, Congress created additional privacy risks for Americans; it did so for a specific foreign intelligence purpose and not with the expectation that a limited foreign intelligence tool would be used freely for domestic law enforcement, overriding stronger Congressional limits in that sphere. While the government disputes the notion that 702 information is frequently used for routine law enforcement, the FBI does not make those numbers publicly available. And the fact remains that under the existing statute the practice is perfectly legal.

Importantly, the FBI Minimization Guidelines only require that queries be designed to extract foreign intelligence information or criminal evidence, and do not limit use of terms that are likely to return sensitive or selective information. The FBI Minimization Guidelines label religious, political, and media activities as “sensitive information,” but do not prevent targeted searching—the Guidelines permit retention, dissemination, and use of any “sensitive information” so long as it appears to be evidence of any crime, and do not comment on or in any way limit use of “sensitive information” as a query term. This rule may prevent retention of non-illicit, embarrassing “dirt,” but it does nothing to prevent selective prosecution. With the existing rules, language connected to protest organizations, religious groups, or press activity could be the basis of a keyword search. This could serve as a “sifting tool” to target groups, facilitating the opening or support of criminal investigations against members of those groups who might be engaged in any illicit activity. The attendant risks of court disclosure of sensitive intelligence information may provide some practical limitations against low-level crimes. The primary method for that limitation, however, are notice requirements to the defendant when the government uses 702 information court. In the past, the Department of Justice had maintained that derivative evidence from 702 did not trigger the notice requirement at all. While that policy has been changed, it is entirely possible the prior interpretation could be restored without public knowledge.

With these factors combined, in the future federal law enforcement may see little practical risk or disincentive in using Section 702 extensively for domestic criminal use, including regarding low-level crimes with no connection to national security.

Furthermore, where important privacy values are at risk, we should not rely on informal constraints. If we agree that Section 702 information should not be used in the investigation of low-level crimes—or for any domestic crimes unrelated to terrorism or posing an imminent harm to human life—then we should expressly prohibit the practice by law. These are sensible reforms, and those who object to them should explain why it would ever be appropriate to engage in these practices instead of merely asserting additional protections are unnecessary.

Use restrictions would reasonably limit law enforcement without recreating the Wall or disrupting the foreign intelligence value of Section 702. The existing ODNI rule could provide the basis for a statutory reform acting as a companion to the “backdoor search loophole” fix, although several revisions are necessary. First, the list of exempt crimes should limited to a set of specific enumerated offenses to provide clarity and prevent overbroad interpretations. Second, the rule should apply to both investigations and in-court use; closing this “fruit of the poisonous tree loophole” is essential given the risks of undiscovered derivative use. The Cybersecurity Information Sharing Act’s use restrictions—which in part permit use of data received “solely for the purpose of preventing, investigating, disrupting, or prosecuting” a set of listed offenses—could serve as an effective model to achieve this (although, naturally, the specific offenses would differ).

Such limits would be consistent with the foreign intelligence objectives of Section 702 and permit FBI use for critical cases to protect national security, while preventing the risk of abuse and co-opted use for low-level crimes totally unrelated to Section 702’s purpose. Use limits are certainly not a complete solution to the problems that Section 702 surveillance poses, but they would do much to remedy the serious privacy and due process concerns that the law raises for Americans. In protecting against abuse that might occur in spite of a limit on U.S. person queries and protecting civil liberties without impairing the foreign intelligence and national security objectives of 702, use limits would be an essential companion reform to closing the backdoor search loophole.

Jake Laperruque is Senior Counsel at The Constitution Project, where he is working on issues of government surveillance, national security and defending privacy rights in the digital age. Prior to joining TCP, Jake was a fellow at New America’s Open Technology Institute and at the Center for Democracy and Technology. He previously served as a law clerk for Senator Al Franken on the Senate Judiciary Subcommittee on Privacy, Technology, and the Law, and as a policy fellow for Senator Robert Menendez. He is a graduate of Washington University in St. Louis and Harvard Law School.